Bias generating circuits utilizing several current paths including transistors coupled together in a current-mirror configuration are widely used. These circuits have two stable operating states, a zero-current state and a steady-current state. When power is turned on the bias generating circuit may settle in either state.
If the circuit settles in the zero-current state it must be forced into the steady-current state.
A standard technique for forcing the bias circuit into the steady-current state during power up is to bleed a small amount of current into a node in a selected one of the current paths. A problem with this technique is that small amount of current continues to flow through the selected current path after the bias circuit is operating and degrades the accuracy of the bias voltage and/or current levels of the output signals.